暂态电压失稳模式的主导不稳定平衡点计算

Computation of Controlling Unstable Equilibrium Point Corresponding to Instability Mode of Transient Voltage

构建了负荷采用三阶感应电动机并联恒阻抗动态模型时电力系统暂态电压稳定分析的数学模型.针对采用牛顿法求取故障后系统电压失稳模式的主导不稳定平衡点(CUEP)存在的初值确定难题,提出了一种实用的解决方案:通过判别给定故障的主导负荷母线,对主导负荷母线以外系统由故障后稳定平衡点处的状态进行戴维南等值,对负荷中感应电动机部分采用其稳态等值电路,再由感应电动机的转矩特性求得CUEP附近的一个点作为迭代初值,以计算CUEP.文中还给出了如何得到更接近CUEP的迭代初值以便更可靠地求得CUEP的方法.IEEE 9节点和39节点系统的计算结果证明该方法可靠有效.

This paper proposes a mathematical model for analyzing the transient voltage stability of power systems whose load is presented by a three-order induction motor paralleling constant impedance model, and gives a practical scheme to choose the initial point when the Newton method is used to compute the control＇ling unstable equilibrium point （CUEP） corresponding to the instability mode of system voltage. In this scheme, the controlling load bus of a given fault is identified, the Thevenin equivalent circuit is used to represent the rest of. the system in the state of post-disturbance stable equilibrium point, the steady equivalent circuit is adopted to describe the induction motor in a composite load, and a point near the CUEP is obtained based on the torque characteristics of the induction motor and is then taken as the initial iteration point. Moreover, a method to obtain the initial iteration point closer to the CUEP is proposed, by which the CUEP can be computed more reliably. Computation results of the IEEE 9-bus and the 39-bus systems show that the proposed method is reliable and effective.